"Based on all the evidence, perhaps the element of mercy was over-exaggerated."

Pistorius' sentence – handed down in Pretoria's High Court in October – was heavily criticised around the world.

Ms Steenkamp's mother, June Steenkamp, admitted her family were "disappointed in the judgement".

"Oscar has to pay for what he has done. He actually did do it and did kill her and he admitted he did that," she said.

"It is not that we want vengeance or for him to suffer with his disabilities.

"We wouldn’t have wanted him to go to jail and be abused and I feel that it is fair."

Polly Neate, chief executive of domestic violence charity Women's Aid, said: "Although we are pleased he has received a custodial sentence, the length of the sentence is worryingly short, given the severity of the crime.

"Violence against women is a very serious issue, and two women a week are killed by a partner or ex-partner in this country alone."

Twitter was flooded by angry users posting with the hashtag #nojustice.

Flint Bedrock wrote: "Oscar Pistorius's sentence is a sick joke."

And Caroline Halley said: "Properly disgusted by Oscar Pistorius's sentencing. What an insult to her family and friends."

The hearing, which was not attended by Pistorius, will continue on Wednesday.